Field of the Invention
The invention relates to a sheet decurler or smoothing device provided in a sheet-processing rotary printing press for smoothing sheets. The sheet decurler includes a suction chamber having a suction connection, and a smoothing notch communicating with the suction chamber. The sheets are to be drawn over the smoothing notch.
Sheets processed by rotary printing presses, in particular after processing thereof in a recto printing process, generally exhibit a certain amount of curvature in the processing direction, which is often particularly pronounced at the trailing end of the sheets. Since that is already disadvantageous for the formation of a sheet pile or stack with accurately aligned edges and, moreover, for subsequent processing steps, heretofore-known rotary printing presses are equipped in particular with decurling or smoothing devices. Corresponding smoothing devices are installed in sheet guide surfaces of deliveries in such printing presses, and generally include a suction chamber provided with a suction connection, and a smoothing notch communicating with the suction chamber.
The processed sheets are drawn over the smoothing notch with the unprinted side of the sheets facing the smoothing notch, so that during operation, i.e., when a vacuum is formed in the suction chamber, a crease or bead is formed in the respective sheets and projects into the smoothing notch, thereby reversing the curvature formed in the respective sheets.
A decurling or smoothing device of that general type is disclosed in German Published, Non-prosecuted Patent Application DE 197 33 692 A1, for example, and is configured in such a way that the vacuum in the suction chamber does not dissipate abruptly when a respective sheet leaves the smoothing notch formed there as a suction gap. For that purpose, the suction chamber including the suction gap is provided with suction openings upstream of the suction gap with regard to the processing direction. The openings are formed and disposed in such a way that, as the trailing edge of a respective sheet increasingly approaches the suction gap, the openings draw more and more leakage air. As a result, only low suction forces continue to act upon the trailing region of a respective sheet drawn over the smoothing notch, so that the result is a quiet sheet run without any turning up of the sheet trailing edge leaving the smoothing notch.
A sheet decurling or smoothing device constructed in that manner is therefore also distinguished by reduced noise development and is suitable, in particular, for decurling moderately deformed and/or flexible sheets. In particular, it is possible to gather from heretofore-known sheet decurlers or smoothing devices the teaching that noise development therefrom may be reduced by avoiding abrupt dissipation of the vacuum of the suction chamber.
It is accordingly an object of the invention to provide a sheet decurler or smoothing device for a sheet-processing rotary printing press, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and in which even greatly deformed and flexurally rigid sheets may be decurled or smoothed with the least possible noise development.
With the foregoing and other objects in view, there is provided, in accordance with the invention, in a sheet-processing rotary printing press, a sheet decurler for smoothing sheets. The sheet decurler comprises a suction chamber having a connection for connecting the suction chamber to a suction source, and a smoothing notch communicating with the suction chamber. The smoothing notch is disposed in such a way that sheets are drawable thereover, and the suction chamber is constructed as a sound muffler.
In accordance with another feature of the invention, the suction-chamber sound muffler is constructed as an impedance sound muffler.
In accordance with a further feature of the invention, the suction chamber forms a returned or reversed flow duct extending transversely to the smoothing notch.
In accordance with an added feature of the invention, the flow duct is formed as a diffusor.
In accordance with an additional feature of the invention, the suction chamber is constructed as a resonance sound muffler.
In accordance with yet another feature of the invention, the sheet decurler further includes a plurality of ducts disposed along the smoothing notch and opening at one end of each thereof into the smoothing notch and at the other end of each thereof into the suction chamber.
In accordance with yet a further feature of the invention, the ducts are formed by hollow profiles projecting into the suction chamber.
In accordance with a concomitant feature of the invention, the suction chamber has a sound-absorbing construction.
Thus, in order to achieve the foregoing object or objects, a sheet decurler or smoothing device having a suction chamber with a connection to suction, and a smoothing notch communicating with the chamber, is provided. The suction chamber is constructed as a sound muffler or silencer.
Through the use of this feature, a noise produced in the suction chamber by a sudden collapse of the vacuum therein is damped or muffled immediately at the point of production. This advantageously permits the maintenance of a vacuum which is sufficiently high for achieving a satisfactory decurling result until the trailing edge of a respective sheet drawn over the smoothing device exposes the smoothing notch.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a decurler or sheet smoothing device in a sheet-processing rotary printing press, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.